The Price of Poor Power Quality Ian C Evans, Harmonic Solutions Co. UK and Michael J Richards, Algozen Corporation, Canada

The Price of Poor Power Quality

Ian C Evans, Harmonic Solutions Co. UK and Michael J Richards, Algozen Corporation, Canada
Abstract 
Electric drives, both DC drives (often called “SCR drives” in the industry) and AC variable frequency drives (VFDs), are commonplace on drilling rigs and offshore installations. Their operation can significantly degrade the quality of electric power, resulting in loss of operational capability, equipment failure with subsequent down-time in addition to presenting safety concerns. Marine classification bodies have rules to limit harmonic voltage distortion but these are rarely policed. The quality and security of electric power are absolutely crucial to the operational integrity of any drilling rig or offshore installation, irrespective of type or class. Any failure or malfunction of equipment due to poor power quality can result in severe or disastrous consequences. This paper looks at the main problems associated with poor power quality, including excessive harmonic voltage distortion, line notching (SCR drives) and voltage spikes attributed to SCR drives; these are all traditional ‘harmonics problems’. However, the introduction of large VFDs has resulted in significant increases in ‘common mode voltage’ problems which can be extremely problematic; even to the point where rigs are being taken off-hire due to major equipment being deemed ‘dangerous’. On another rig, the gas detection system failed when the top drive VFD was running due to this problem. This paper will provide a practical understanding of each problem and how they can be resolved. The paper also introduces an inexpensive, yet powerful, remote power quality monitoring system which can be easily retrofitted to monitor all aspects of land-rig and offshore rig power quality, including waveforms and harmonic spectrums. The data is available locally with the capability to transmit the information via the internet to anywhere in the World.

LINK FULL PAPER ORIGINAL
https://www.google.com.br/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0CC4QFjAC&url=http%3A%2F%2Fwww.aade.org%2Fapp%2Fdownload%2F6857647004%2FAADE-11-NTCE-07.pdf&ei=QnSpVKLzJdOTNtLxgogH&usg=AFQjCNHm05m6r6W9vVUSJZlCLLT4ATHEkQ&sig2=DuFagJEuZCRiGxGxUUqrig

LINK ALTERNATIVE
https://copy.com/fyS9nLkVUXPffmPB

Harmonics Reduction Techniques in Renewable Energy Interfacing Gonverters Ali M. Eltamaly, Ph.D King Saud University Saudi Arabia

INTRODUCTION
 In the recent years there has been growing interest in renewable energy generation along with growing demands for development of a suitable interface system. Low harmonics in line current of the converters used in the utility interface.
  Controlled and uncontrolled converters are used widely in the utility interface of renewable energy systems to reduce cost, harmonic contents in line currents. A detailed third harmonic current injection technique reduce the harmonic contents in line currents of controlled and uncontrolled converters that used in renewable energ'y applications. The approach is based on circulaling third harmonic current from DC link current to line currents of controlled and uncontrolled converters to reduce its THD. A new injected current shape is computed from analysis to achieve sinusoidal utility line currents. A controllable single switch boost converter conrrccted in shunt is employed to circulate the new injected current shape. A method to implement the proposed approach under varying load condition is shown. Analysis,d esign,l imitations,s imulationa nd experimentarl esult are presented. In modern Power electronics converters, three-phase controlled converter is commonly used.

LINK FULL PAPER
http://faculty.ksu.edu.sa/eltamaly/Documents/[3].pdf

LINK ALTERNATIVE
https://copy.com/IApswwIOUqPR0xNt

Study on the component analysis of harmonic current to specify the cause of fault in electrical power line Author Park, Chan Heon

 ABSTRACT

Development of power semiconductors has promoted to the advancement of large static power converters. Due to use of these converters, the power quality has become a very important and highly controversial issue in today's industrial environments. Converters of the supplied 60Hz ac to dc or to variable frequency ac power offers more precise speed control and increased efficiencies for many industrial processes. These advantages have accelerated wide spread usage of static power converters. However, these advantages cause disadvantages of increased sensitivity to both the quality of power supplied by the utility and the quality of the power inside the industrial facility. With these trends of industrial environments, both electric utilities and end users of electric power are increasingly concerned about quality of electric power. And the harmonic problem becomes one of the most important issues on the power quality problems. Therefore, this thesis aimed to represents theoretical study, occurence examples, and countermeasure of harmonics. Therefore, in this thesis also introduces terms and generation of harmonics characters based on different loads and clarified the areas of harmonic problems on the industrial facilities. In end of this thesis, it has been discussed for controlling of harmonics. Chapter 3 provided the guidelines for the harmonics level referenced from Korea, Japan, and IEEE std 519-1992. In chapter 4, this thesis presents the results of example study as regards a fault owing to OCGR(Over Current Ground Relay) and another fault owing to N phase line in main transformer of substation. Chapter 5 illustrates the delivered reference for power filters, and suggest real time PQM(Power Quality Management) system to diagnosis harmonics. This paper wishes to express that these study results may contribute to localization of power filters and to resolution of harmonic problems.

Design of an LCL-Filter for the Three-Parallel Operation of a Power Converter in Wind Turbines DONG-KEUN YOON AJOU UNIVERSITY

Permanent Magnet Synchronous Generators (PMSG) are widely used in variable-speed wind turbines. However, the power devices must support high currents to get their high-power rating because the PMSG is connected directly to the grid through a back-to-back converter. Therefore, the rated current of the power device can be reduced to one third of the rated value by using a three-parallel operation. The low switching frequency of a high power system may cause an increase in the harmonics found in the output current.
This paper proposes a design scheme for an LCL-filter used for three-parallel operation of a power converter in 2MW-wind turbines. An appropriate design method of the delta configured LCL-filter is also proposed to improve the output power quality in the system. A novel design method for the inner inductance of the LCL-filter is proposed in order to overcome the existing trial and error methods used in designing the filter. LCL-filters typically have a problem with a reduced power factor (PF), due to the capacitor used. To improve the poor PF, a simple compensation method is also proposed. The simulation and experimental results demonstrate that the grid current harmonics are low and the PF is improved.

Research on High Efficiency Non-Isolated Push-Pull Converters with Continuous Current in Solar-Battery Systems Yan Li, Trillion Q. Zheng, and Qian Chen

Research on High Efficiency Non-Isolated Push-Pull Converters with Continuous Current in Solar-Battery SystemsYan Li, Trillion Q. Zheng, and Qian Chen
Abstract
 In order to improve the output efficiency of solar cells and to extend the life span of batteries, the input currents of converters are required to be continuous. If low output voltage ripple is required at the same time, it is obvious that the application of basic two-order converters (such as Buck and Boost derived converters) will not be good enough. In this paper, a lot of non-isolated push-pull converters (NIPPCs) with continuous current will be introduced due to their lower current stress, higher efficiency and better EMC performance. By decomposing the converters into push-pull cells, inductor and free-wheeling diodes, two families of NIPPCs based on single inductor and coupled inductor separately are systematically generated. Furthermore, characteristics analyses for some of the generated converters are also shown in this paper. Finally, two prototypes based on the corresponding typical topologies are built in the lab to verify the theoretical outcomes.
LINK
http://jpe.or.kr/archives/view_articles.asp?seq=852